OK, so you’ve made the Ru complexes. Now, how are you going to determine what it does with DNA? Will your complex bind DNA, like this? Will the other complexes also bind DNA? Will the other complexes cleave DNA? Will your complex cleave (damage) DNA?

How might their different structures affect their behavior with DNA? Electronic Spectroscopy (UV/vis) Cyclic Voltammetry (E red )

Electronic Spectroscopy The Ru complexes are all orange: Won’t their UV/vis spectra be the same?

Cyclic Voltammetry A Method to Measure Electrochemical Behavior and E red Will the complexes have different Ru redox potentials?

The Same Question will be asked of your hemes: Can changing Heme substituents vary Fe(3+/2+) reduction potentials?

The Cyclic Voltammetry Experiment

+ current, cathodic i c - current, anodic i a + potential, V - potential, V

+ current, cathodic i c - current, anodic i a + potential, V - potential, V Reduction Oxidation

+ current, cathodic i c - current, anodic i a + V- V- V +1.0 V -1.0 V When no electroactive species is present, no current flows, no i c nor i a This is what background electrolyte should look like.

+ current, cathodic i c - current, anodic i a + V- V- V +1.0 V-1.0 V Starting at a + V, Initially no current flows

+ current, cathodic i c - current, anodic i a + V- V- V +1.0 V-1.0 V If a reducible species is present i c will increase

+ current, cathodic i c - current, anodic i a + V- V- V +1.0 V-1.0 V And continue to increase

+ current, cathodic i c - current, anodic i a + V- V- V +1.0 V-1.0 V Until all of the species is reduced. i c has reached a maximum.

+ current, cathodic i c - current, anodic i a + V- V- V +1.0 V-1.0 V Then i c decreases until…

+ current, cathodic i c - current, anodic i a + V- V- V +1.0 V-1.0 V It again reaches the background current level.

+ current, cathodic i c - current, anodic i a + V- V- V +1.0 V-1.0 V Now the potential is reversed

+ current, cathodic i c - current, anodic i a + V- V- V +1.0 V-1.0 V And as V is more positive, the reduced species can be re-oxidized

+ current, cathodic i c - current, anodic i a + V- V- V +1.0 V-1.0 V So i a decreases to a maximum

+ current, cathodic i c - current, anodic i a + V- V- V +1.0 V-1.0 V Where all has been oxidized,

+ current, cathodic i c - current, anodic i a + V- V- V +1.0 V-1.0 V Then i a decreases, back to the background level.

+ current, cathodic i c - current, anodic i a + V- V- V +1.0 V-1.0 V Important features: EcEc EaEa

+ current, cathodic i c - current, anodic i a + V- V- V +1.0 V-1.0 V E 1/2 is ~ E o Red EcEc EaEa E 1/2

+ current, cathodic i c - current, anodic i a + V- V- V +1.0 V-1.0 V All Fe(3+) Using an Fe(3+) heme, Fe is electroactive, (and also the heme!) …

+ current, cathodic i c - current, anodic i a + V- V- V +1.0 V-1.0 V A little Fe(2+) formed

+ current, cathodic i c - current, anodic i a + V- V- V +1.0 V-1.0 V more Fe(2+) formed

+ current, cathodic i c - current, anodic i a + V- V- V +1.0 V-1.0 V Largest cathodic current, Max rate of Fe(2+) formed

+ current, cathodic i c - current, anodic i a + V- V- V +1.0 V-1.0 V Little Fe(3+) left; Less Fe(2+) forms; Decrease in i c

+ current, cathodic i c - current, anodic i a + V- V- V +1.0 V-1.0 V all Fe(2+) now

+ current, cathodic i c - current, anodic i a + V- V- V +1.0 V-1.0 V

+ current, cathodic i c - current, anodic i a + V- V- V +1.0 V-1.0 V A little Fe(2+) is re-oxidized to Fe(3+)

+ current, cathodic i c - current, anodic i a + V- V- V +1.0 V-1.0 V

+ current, cathodic i c - current, anodic i a + V- V- V +1.0 V-1.0 V Nearly all Fe(2+) has been oxized

+ current, cathodic i c - current, anodic i a + V- V- V +1.0 V-1.0 V All back to Fe(3+). Cycle could be run again, many times.

+ current, cathodic i c - current, anodic i a + V- V- V +1.0 V-1.0 V Important features: EcEc EaEa

+ current, cathodic i c - current, anodic i a + V- V- V +1.0 V-1.0 V E 1/2 for Fe(3+/2+) reduction EcEc EaEa E 1/2

the black box Working Electrode: Where the redox reaction action occurs

the black box Reference Electrode: Defines “0” potential for the cell. We use Ag/AgCl Working Electrode: Where the redox reaction action occurs

the black box Auxilliary Electrode: Needed to complete circuit. We use a Pt wire Reference Electrode: Working Electrode: Where the redox reaction action occurs

the black box Fe(3+) At start of CV experiment… Working Electrode: Where the redox reaction action occurs

the black box Working Electrode: Where the redox reaction action occurs Fe(2+)Fe(3+) Moving up the cathodic current peak…

the black box Working Electrode: Where the redox reaction action occurs Fe(2+)Fe(3+) Fe(2+) Fe(3+) Still moving up the cathodic current peak…

the black box Working Electrode: Where the redox reaction action occurs Fe(2+) Fe(3+) Fe(2+) Fe(3+) After the maximum cathodic current peak…

the black box Working Electrode: Where the redox reaction action occurs Fe(2+)Fe(3+) Fe(2+) Fe(3+) Moving down the anodic current peak…

the black box Working Electrode: Where the redox reaction action occurs Fe(2+)Fe(3+) Sill moving down the anodic current peak…

the black box Working Electrode: Where the redox reaction action occurs Fe(3+) At end of CV experiment…

+ ic+ ic - ia- ia - V- V In your CV scans of Fe(porphyrin)Cl, you will see: Interpretation???? + V

+ ic+ ic - ia- ia - V- V One more thing: Use of internal reference, ferrocene E(1/2) values of sample are reported vs. ferrocene (example….) + V

Schedule for Thursday Nov. 1 CVUV/vis 1:00 -1:20Group 1Group 2 1:20 – 1:35Group 2Group 1 1:35 – 1:50Group 3Group 4 2:00 – 2:15Group 4Group 3 2:15 – 2:30Group 5Group 6 2:30 -2:45Group 6Group 5 2:45 – 3:00Group 7 After that: 3:30 Everyone meet in 264 to discuss results 4:15 – Attend Seminar by Dr. Nathanial Nucci Calculate E(1/2) for your data immediately, both vs. reference and corrected, vs. ferrocene

How is the range of Heme Potentials in Respiration adjusted?